Uninterruptible Power Supply Systems
Cross-references point to the standards that now own the topic after the October electrical rewrites: MV cable to medium-voltage-cables, energy storage to battery-energy-storage-systems, service grounding to grounding-and-bonding, lightning to lightning-protection.
Showing changes from Rev 4
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in Uninterruptible Power Supply Systems.
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title: Uninterruptible Power Supply Systems
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description: >
When to use: Static (solid-state) uninterruptible power supply (UPS) systems that protect critical AC electrical loads — data processing and IT equipment, network and communications gear, life-safety and process controls, medical equipment, and other loads that cannot tolerate a power interruption or a sag — from utility disturbances, sags, surges, and outages. Covers single-phase and three-phase units of small (point-of-use), medium, and large (data center and facility) ratings; topology selection per IEC 62040-3 (double-conversion VFI, line-interactive VI, standby VFD); transformer-free and transformer-based designs; VRLA and lithium-ion battery energy storage with runtime sizing per IEEE 1184; internal static bypass and external maintenance (wraparound) bypass; redundancy from a single module through N+1, parallel, and dual-bus/2N; input harmonics and output performance for nonlinear loads; efficiency and energy-saver/eco modes; monitoring, communications, and emergency power off; seismic anchorage; and the room and code requirements the unit imposes.
− Not intended for: DC battery and charger plants that supply switchgear control power ([[sync/dc-battery-systems]]); engine generators that provide the long-duration standby source behind a UPS ([[sync/generators]]); automatic transfer switches that select between sources ([[sync/automatic-transfer-switches]]); surge protective devices ([[sync/surge-protective-devices]]); rotary and flywheel (kinetic energy storage) UPS, which are a separate technology; and stationary energy storage systems intended for load shifting, peak shaving, or grid support, which are specified to NFPA 855 and UL 9540 as energy storage rather than as a UPS.
+ Not intended for: DC battery and charger plants that supply switchgear control power ([[sync/dc-battery-systems]]); engine generators that provide the long-duration standby source behind a UPS ([[sync/generators]]); automatic transfer switches that select between sources ([[sync/automatic-transfer-switches]]); surge protective devices ([[sync/surge-protective-devices]]); rotary and flywheel (kinetic energy storage) UPS, which are a separate technology; and stationary energy storage systems intended for load shifting, peak shaving, or grid support, which are energy storage under NFPA 855 and UL 9540 rather than a UPS (see [[sync/battery-energy-storage-systems]]).
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## A maintenance and replacement contract should be considered for mission-critical UPS systems, because the battery is a consumable with a defined service life and the system's value depends on the battery being replaced before it fails an in-service discharge. {note}